Solenoid

ABSTRACT

A solenoid assembly has a U-shaped magnetic frame of sheet metal and a T-shaped magnetic plunger of laminated construction movably mounted within the solenoid coil. The crossbar portion of the Tshaped plunger is slideably and tiltably attached to the stem portion thereof to permit the crossbar portion to engage the upper edges of both legs of the U-shaped frame in spite of manufacturing inaccuracies affecting the relative positions of said upper edges. The crossbar portion of the plunger is spring loaded in a manner to urge the crossbar toward the upper edges of the legs of the U-shaped frame, and the stem of the plunger is of such length as to permit the crossbar portion of the plunger to contact said upper edges shortly before the bottom of the stem contacts the base of the frame.

Schantz et al.

[ Oct. 28, 1975 SOLENOID [75] Inventors: Spencer Craig Schantz, New Berlin;

William Ray Berry, Menomonee Falls, both of Wis.

[73] Assignee: Spencer C. Schantz, New Berlin,

Wis.

[22] Filed: July 29, 1974 [21] App]. No.: 492,808

3,505,628 4/1970 Allen 335/262 Primary Examiner-Harold Broome Attorney, Agent, or FirmArthur L. Morsell, Jr.

571 ABSTRACT A solenoid assembly has a U-shaped magnetic frame of sheet metal and a T-shaped magnetic plunger of laminated construction movably mounted within the solenoid coil. The crossbar portion of the T-shaped plunger is slideably and tiltably attached to the stem portion thereof to permit the crossbar portion to engage the upper edges of both legs of the U-shaped frame in spite of manufacturing inaccuracies affecting the relative positions of said upper edges. The crossbar portion of the plunger is spring loaded in a manner to urge the crossbar toward the upper edges of the legs of the U-shaped frame, and the stem of the plunger is of such length as to permit the crossbar portion of the plunger to contact said upper edges shortly before the bottom of the stem contacts the base of the frame.

12 Claims, 5 Drawing Figures 1 SOLENOID BACKGROUND OF THE INVENTION This invention relates to solenoids such as are used for the purpose of opening and closing valves or for performing other types of mechanical work in response to an electrical signal. More particularly, this invention relates to solenoids that have a U-shaped magnetic frame with a T-shaped magnetic plunger movably mounted within the frame. In such solenoids, a problem of buzzing has been encountered in the past, due to manufacturing inaccuracies at the three areas where the T-shaped plunger contacts the U-shaped frame, these areas being the edges of the two legs and the base of the frame. In the past, this problem has been alieviated by precision grinding the areas of contact between the plunger and frame to provide a close enough fit to eliminate the buzzing. However, this precision grinding is expensive.

SUMMARY OF THE INVENTION This invention provides for a tiltable, movable mounting of the crossbar portion of the T-shaped plunger on the stem thereof to permit relative movement so that the crossbar can readily compensate for manufacturing inaccuracies and thus insure a proper engagement of the three contact areas. This eliminates buzzing without the necessity of precision grinding.

DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevational view of one illustrative embodiment of the invention with the plunger in its withdrawn position;

FIG. 2 is a side view taken on the line 22 of FIG. 1;

FIG. 3 is a longitudinal sectional view taken on the line 3-3 of FIG. 2 with the plunger in its actuated position;

FIG. 4 is a perspective view of the plunger alone; and

FIG. 5 is a cross-sectional view through the plunger.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIGS. 1 and 3, the preferred embodiment of the invention has a substantially U-shaped magnetic frame including spaced sides or legs 12 and a bottom or base 14. A coil 16 which is wound upon a bobbin 18 (FIG. 3) is supported within U- shaped frame 10. Bobbin 18 is made out of insulating material and has a lower flange 20 and an upper flange 22 to protect the ends of coil 16. The upper edges of the frame sides 12 have projecting lugs 26 which are bent over FIG. 1 to press against upper flange 22 and hold bobbin 18 and coil 16 in assembled position by maintaining the dowelled connection betweenthe base 14 and the lower flange 20 of the bobbin in the assembled condition shown in FIG. 3.

The ends of coil 16 are coupled to conventional electrical terminals 28 which project from the side of frame 10 as shown in FIG. 1.

The bobbin 18 has a central bore 30 (FIG. 3) within which the stern portion 32 of a T-shaped plunger 34 is slideable. Plunger 34 is suspended from a spring 36 which is attached to a fixed frame member 38. A movable arm 40 which may be attached to a valve or to a mechanical linkage (not shown) is attached by suitable means 42 (FIG. 2) to openings 44 in the upper portion of stem 32. A spring 36 normally urges the plunger 34 to the withdrawn position shown in FIG. 1.

When electrical current is passed through coil 16, the magnetic field of coil 16 and frame 10 draw plunger 34 downward to the position shown in FIG. 3, thereby stretching spring 36 and moving arm 40 downward to perform mechanical work, e.g. to open a water valve in an automatic washer. When the current flow through coil 16 is terminated, plunger 34 is returned to the position shown in FIG. 1 by spring 36.

The principal problem to which this invention is addressed is the problem of buzzing at the areas where the T-shaped plunger 34 contacts the U-shaped frame 10. This occurs at the upper edges 24 of sides 12 and at the center 46 FIG. 3 of base 14.

The above-described solenoid is an AC. solenoid in which the magnetic field changes direction times per second. With normal manufacturing inaccuracies, there is usually enough of a gap between one or more of the areas where the plunger 34 contacts the frame 10 to permit the plunger to vibrate when the magnetic field reverses, thereby producing a 60 cycle buzz. In the past, this problem has been overcome by precision grinding of the surfaces where the plunger 34 and frame 10 meet to thereby reduce the gaps below the level that would permit buzzing. However, this is relatively expensive and the principal object of this invention is to provide a less expensive means of eliminating such buzzing. This is accomplished by providing a slideable and tiltable mounting for the crossbar portion of T-shaped plunger 36.

Referring to FIGS. 1 and 2, the crossbar portion 48 of T-shaped plunger 34 has a central opening 50 which is slightly larger than the external cross-sectional dimensions of the stem 32 of plunger 34. The central opening 50 of crossbar portion 48 is free to slide up and down and to tilt on stem portion 32. A clip 52 (FIG. 4), which engages a slot 54 in stem portion 32, limits downward movement and projecting flange portions 56 'at the top of the outer laminations of stem portion 32 limit movement in an upward direction. Between clip 52 and flanges 56, crossbar portion 48 may be moved up and down and tilted as shown in FIG. 3 at an angle such as the angle A when necessary to make firm contact with the upper edges 24 of frame sides 12, to

'thus compensate for manufacturing inaccuracies. The

tiltability can be controlled by the dimensions of opening 50, which are selected to be large enough to permit tilting-at any angle that will be necessary to overcome machining inaccuracies in the position of edge 24.

A spring 58 normally urges crossbar portion 48 toward the edges 24 and toward the base 14 of frame 10. In the actuated position of plunger 34, shown'in FIG. 3, spring 58 presses crossbar portion 48 down upon edges 24. r

The stem portion 32 of plunger 34 is of such length as to contact the bottom 14 of frame 10 after the crossbar portion 48 of plunger 34 contacts the edges 24 of frame 10. Thus the end of stem portion 32 of plunger 34 does not contact the bottom 14 of frame 10 until the spring 58 has been compressed. When coil 16 is deenergized, spring 58 lifts stem portion 32 out of contact with the bottom 14 of frame 10, thereby breaking the magnetic circuit therebetween. In the past, this was done by a separate spring within opening 30.

' nated frame. By referring to FIG. 5, it will be noted that the outer lamination on each side of the plunger 34 is of less width throughout the major portion of its length than the laminations therebetween. Thus the crosssection of the plunger as shown in FIG. 5, while generally rectangular, more closely approximates acircle because of the less: width of the outer laminations. By approximating the circular cross-section, increased effi ciency results. The upper end portions of the outer lam- --ina t'i0ns are of greater 'width to provide the projecting flange portions 56 which form of the spring '58. y I

Various changes" and modifications may be made without departing from the spirit of the invention, and all of such. changes --are contemplated as may come a seat for the upper end within the scope of theclaims'.

What we claim is: 1. In a solenoid assembly having a coil, having a magnetic frame including spaced side members embracing said coil and including a base on which the coil is supported, and there being a T-shapedmagnetic plunger including a cross-bar portion and a stem portion mounted for movement toward and away from said base',"the improvement wherein said cross-bar portion of said plunger is loosely mounted on said stem portion "for both-slideable and tiltable movement to permit said crossbar portion to adjust itself for proper seating on the upper edges of both sides of said frame in spite of manufacturing inaccuracies affecting the relative position of said edges, said crossbar portion comprising a 'flat 'sheet of magnetic material having an opening 2, A- solenoid as claimed in claim 1 in which the J length of said stem portion is such that the tiltable and slideable mounting of the crossbar portion allowsjthe lower end of said ste'm portion to contact the base while the ends, of the crossbar portion are seating on the upper edges of the sides.

A solenoid as claimed in claim 2 and further comprising spring means normally urging'said crossbar portion of said T-shaped plunger toward said upper edges of the sides.

we 4". A; solenoid as claimed in claim 3 wherein the lengthaof said stem portion of said plunger is such that the lower end of said stem portion does not contact the ba eofqsaid frame until after said spring means has been, compressed, whereby said spring means serves to break the magnetic circuit between said plunger and the bottom of said frame when said coil is de-energized. 5. A solenoid as claimed in claim 1 wherein said plunger islaminated and said frame is solid.

'6. In a'solenoid assembly having a coil, having a magnetic .frame including spaced side members embracing said coil and including a base on which the coil is supported, and therebeing a T-shaped magnetic plunger including .a crossbar portion and a stem portion mounted for movement toward and away from said base, the improvement wherein said crossbar portion of said plunger is loosely mounted on said stem portion for both slideable and tiltable movement topermit said crossbar portion to adjust itself for proper seating on the upper edges of both sides of-said frame in spite of manufacturinginaccuracies affecting the relative posi .tion of said edges,- said crossbar portion comprising a hat sheet of magnetic material having an opening therein which is slightly larger than the cross-sectional dimensions of said stem portion, said crossbar portion being fitted over said stem portion, and further comprising stop means at the upper end of said stem portion, and a removable clip on said stem portion below said crossbar portion limiting movement in the other direction. a 1 I Y 7.-'A solenoid as claimed in claim 6 and further comprising spring means around said stem portion between said upper end stop means and said crossbar portion, said spring means urging said crossbar portion away from said stop means. e

s. A solenoid as claimed inclaim 1 in which there is -a dowelled connection between the base of the magnetic frame and-the lower bobbin flange, and in which the upper edge of each side member has spaced projecting lugs which are bent over to retain the coil in position on the base by maintaining the dowelled connection in engaged condition.

9. A solenoid as claimed in claim 1 in which the upper edge of eachside member has spaced projecting lugswhich are bent over to retain the coil in position on the base, and in which the ends of the crossbar seat onsaid upper edges of the side members between said lugs. f.

10. A solenoid asclaimed in claim 1 wherein said plunger is laminated and wherein the outer laminations are'of less width than the laminations therebetween to more closely approximate a circle in cross-section.

11. A solenoid as claimed in claim 6 in which the plunger is laminated and in which the outer laminations are of less width than the laminations therebetween throughout the length of the stem portion, and in which 

1. In a solenoid assembly having a coil, having a magnetic frame including spaced side members embracing said coil and including a base on which the coil is supported, and there being a T-shaped magnetic plunger including a cross-bar portion and a stem portion mounted for movement toward and away from said base, the improvement wherein said cross-bar portion of said plunger is loosely mounted on said stem portion for both slideable and tiltable movement to permit said crossbar portion to adjust itself for proper seating on the upper edges of both sides of said frame in spite of manufacturing inaccuracies affecting the relative position of said edges, said crossbar portion comprising a flat sheet of magnetic material having an opening therein which is slightly larger than the cross-sectional dimensions of said stem portion to receive the latter, and there being means on the stem portion for limiting slideable movement of the crossbar portion in both directions.
 2. A solenoid as claimed in claim 1 in which the length of said stem portion is such that the tiltable and slideable mounting of the crossbar portion allows the lower end of said stem portion to contact the base while the ends of the crossbar portion are seating on the upper edges of the sides.
 3. A solenoid as claimed in claim 2 and further comprising spring means normally urging said crossbar portion of said T-shaped plunger toward said upper edges of the sides.
 4. A solenoid as claimed in claim 3 wherein the length of said stem portion of said plunger is such that the lower end of said stem portion does not contact the base of said frame until after said spring means has been compressed, whereby said spring means serves to break the magnetic circuit between said plunger and the bottom of said frame when said coil is de-energized.
 5. A solenoid as claimed in claim 1 wherein said plunger is laminated and said frame is solid.
 6. In a solenoid assembly having a coil, having a magnetic frame including spaced side members embracing said coil and including a base on which the coil is supported, and there being a T-shaped magnetic plunger including a crossbar portion and a stem portion mounted for movement toward and away from said base, the improvement wherein said crossbar portion of said plunger is loosely mounted on said stem portion for both slideable and tiltable movement to permit said crossbar portion to adjust itself for proper seating on the upper edges of both sides of said frame in spite of manufacturing inaccuracies affecting the relative position of said edges, said crossbar portion comprising a flat sheet of magnetic material having an opening therein which is slightly larger than the cross-sectional dimensions of said stem portion, said crossbar portion being fitted over said stem portion, and further comprising stop means at the upper end of said stem portion, and a removable clip on said steM portion below said crossbar portion limiting movement in the other direction.
 7. A solenoid as claimed in claim 6 and further comprising spring means around said stem portion between said upper end stop means and said crossbar portion, said spring means urging said crossbar portion away from said stop means.
 8. A solenoid as claimed in claim 1 in which there is a dowelled connection between the base of the magnetic frame and the lower bobbin flange, and in which the upper edge of each side member has spaced projecting lugs which are bent over to retain the coil in position on the base by maintaining the dowelled connection in engaged condition.
 9. A solenoid as claimed in claim 1 in which the upper edge of each side member has spaced projecting lugs which are bent over to retain the coil in position on the base, and in which the ends of the crossbar seat on said upper edges of the side members between said lugs.
 10. A solenoid as claimed in claim 1 wherein said plunger is laminated and wherein the outer laminations are of less width than the laminations therebetween to more closely approximate a circle in cross-section.
 11. A solenoid as claimed in claim 6 in which the plunger is laminated and in which the outer laminations are of less width than the laminations therebetween throughout the length of the stem portion, and in which said outer laminations are of greater width at the upper end to provide projecting flanges forming said upper end stop means.
 12. A solenoid as claimed in claim 6 in which there is spring means between said stem portion and said upper end stop means on said crossbar portion normally urging said crossbar portion away from said upper end stop means. 